There has been a demand for reducing power consumption of system as a whole in recent years. Accordingly, power consumption of computing devices as parts of such systems also needs to be reduced. For example, a power consumption reduction technique of suppressing total power consumption by repeating operation of lowering power to be supplied to a processor element itself when a CPU is not operating and resuming supply of power when operation is resumed has been considered.
Furthermore, even when the CPU is operating, power consumption can be further reduced by suppressing power consumption of a part of a cache in the CPU that is not being used. For example, it is possible to lower the power consumption by controlling power supplied to each way in a cache and stopping supply of power to ways that are not being used even when the CPU is operating.
If, however, a way to which supply of power is stopped is attempted to be driven when a request for reading or writing data is received, there are disadvantages that it takes time to restore the way to an operable state and that good performance cannot be obtained.